1. Field of the Invention
The present invention relates to a semiconductor device used, e.g., as a multiband amplifier for portable terminals.
2. Background Art
Japanese Laid-Open Patent Publication No. 2005-269129 discloses a switch circuit for directing RF signals in different frequency bands to respective different output paths. This switch circuit is configured of a plurality of field effect transistors.
Switches for portable terminals are typically configured of enhancement field effect transistors (FETs), since portable terminals use a single battery which supplies a positive potential. A positive DC bias voltage is applied between the drain and the source of each field effect transistor, and an RF signal passes along the path (or channel) between the drain and the source. Application of a positive voltage to the gate of the field effect transistor opens the channel between the drain and the source (that is, causes the channel to be conductive), whereas application of zero voltage to the gate closes the channel between the drain and the source (that is, causes the channel to be nonconductive).
It should be noted that DC blocking capacitors must be connected to the input and the outputs of each switch to prevent leakage of the DC bias voltage described above. The DC blocking capacitors described in the above publication are configured of surface mount device (SMD) components.
It is desirable to reduce the size of semiconductor devices as much as possible. In the case of semiconductor devices having a switch therein, however, the size of the DC blocking capacitors for the switch substantially contributes to the overall size of the semiconductor device if these DC blocking capacitors are configured of SMD components.